HDR Photography Tip: Shadowmapping

One of my favorite techniques that I use on many HDR images is a trick I call Shadowmapping. Credit goes to Christian Bloch for this technique, although I’ve made a few changes to the original recipe to suit my personal style. I use this primarily with Photomatix Pro from HDRsoft, but have also pulled it off using HDR Expose and HDR Express from Unified Color.

This can get a little involved, and screenshots are helpful. If you’re interested, please see the link to the full tutorial at the bottom of this post.

To start, merge your set of brackets in the usual fashion, but be sure to save the HDR file (Radiance, OpenEXR, etc.) before going into the tonemapping process, as you’ll be opening that file several times.

Once you’ve saved the 32-bit HDR file, tonemap it with the default settings to get a baseline version of your image. Save the output as a 16-bit TIF file with a filename that includes “default” but do not load it into Photoshop, yet. You’ll notice that like many tonemapped images, this one looks a little flat.

Close that window, and in the Photomatix File menu, choose File -> Open and open the HDR file again.

Now, make a “vivid” tonemap of your set. For this version, feel free to pump up the saturation — 75% is about where you’d like to be — along with Luminosity and Microcontrast. Play around the other settings to make it look vivid and over-the-top, but without creating major artifacts (halos, grain, etc.) You want this tonemap to be colorful, sharp, and wild. When done, generate the tonemap and save it off with a filename that includes “vivid.”

Now comes the “secret” Shadowmap iteration.

Send the HDR through tonemapping again, but drop the Saturation to 0, lower the Strength a bit, and set the White Point and Black Point to the maximum. You could also adjust the Black Clipping point, just don’t crush the blacks. Tinker around with other settings at will; the intent is to get a super-high-contrast, black & white version of your image, highlighting all the shadows and highlights with as much pure white and black as possible, without bringing in too many shades of gray. You might also want to drop smoothing down to a minimum to set these shadows, but that depends on the subject. Save the tonemap with a name that includes “shadowmap.”

Now comes the fun part: Load all three tonemaps — Default, Vivid, and Shadowmap — into Photoshop. I prefer to load these images into separate tabs, rather than as layers.

Moving to the Shadowmap file, copy the entire image, then go to the Vivid tab and and paste it as a new layer over the Vivid tonemap. Change the blending mode of the new Shadowmap layer to Hard Light and set the opacity of the that layer to about 30-40%. Clearly, no two images are alike, so you should feel free to play around with different blending modes and opacity settings.

This is where we’re at with the above layer settings of Hard Light at 40%:

The effect is obvious here. Details are sharper, more defined, with higher contrast and more pronounced shadows and highlights. It really helps to pull attention to details and gives the image depth. You can also incorporate your ‘default’ tonemap image in the same way, or use parts of it using layer masking. From here, I’d apply more post-processing to finish the image, but it’s a good place to start.

So, there you have it. I would probably work this image a bit further to galvanize a few details, but this is essentially the “Shadowmapping” technique. It’s a far cry from the original tonemapped version, I’d say.

greg urbano

Good idea. I sometimes get part-way through an image in Photoshop and think it needs a little more bite. So I save a snap of the image in ‘History’ and then use the Find Edges or the High Pass filters to make a new layer and blend them.